KNX TP topology validator
Choose a model: classic TP-64 (64 devices per segment, up to 4 segments per line with repeaters) or one all-TP-256 segment (up to 256 devices). Both models allow 15 secondary lines per area and 15 areas.
Segment capacity depends on the model: 64 interfaces for TP-64, 256 for fully compatible TP-256. Coupler and repeater interfaces count too. An acceptable total can hide an overloaded segment; verify the actual distribution.
Mixed TP-64/TP-256 installations depend on product electrical loads and are not calculated here.
Explore the topology
Select a level. This diagram shows logical hierarchy, not a wiring plan.
0.0.x connects areas through area couplers A.0.0. Area number 0 is reserved for the backbone.
60 bus interfaces per line, including couplers and repeaters.
Three worked examples
1. A simple line
1 area × 1 line × 40 participants = 40. One segment is enough in this model, subject to current and distance checks.
2. An extended line
1 area × 2 lines × 100 participants = 200. Two segments per line are needed: account for repeaters and their power supplies.
3. Multiple areas
2 areas × 3 lines × 180 participants = 1,080. Three segments per line meet this simplified calculation. Main/backbone line participants are excluded from this total.
Find the error
A TP1-64 line has 90 participants on one segment. A learner suggests adding a power supply to exceed the limit. Is that enough?
How to use
Sources and scope
References: KNX Basic documentation, Topology chapter, and KNX TP1 System Specifications. Check the edition, TP1 device type and manufacturer datasheets. Cable distances and current capacity require separate checks.
KNX Association — new TP1-256 topologySiemens — distances and cable lengths (CE1P3127en, central supply, KNX-specified cable)Put your KNX Basic knowledge into practice
10 explained practice questions, no sign-up. Find your first topics to revisit.